Genetic characterization of co-trimoxazole non-susceptible Streptococcus pneumoniae isolates from Indonesia

We investigated the genetic variation of folA and folP genes encoding dihydropteroate synthase (DHPS) and dihydrofolate reductase (DHFR) enzymes amongst trimethoprim/sulfamethoxazole (co-trimoxazole) non-susceptible Streptococcus pneumoniae isolated from the Indonesian population. Archived S. pneumoniae isolates were screened for the presence and analysis of folA and folP genes using the polymerase chain reaction sequencing method. We found that 80 % of co-trimoxazole non-susceptible isolates (n=30/39) showed a 6 bp insertion in the sulphonamide-binding site of DHPS. The Asp-92-Ala and Ile-100-Leu substitutions were more common on DHFR (42 %; 22/53) followed by the Asp-92–Ala, Glu-94–Asp and Ile-100–Leu substitutions (32 %; 17/53). The combination of the Ile-100–Leu substitution at the DHFR region and the 6 bp insertion was the most dominant combination among isolates having both folA and folP genes.